Chore: Mypy work going on

Fix: Recipes costing of semi items would show very high cost of the whole recipe for per unit as ingredient

overlord/src/app/cash-flow/cash-flow.ts

@@ -10,7 +10,7 @@ export class CashFlow {
     details: CashFlowItem[];
   };
 
-  footer?: CashFlowItem[];
+  footer: CashFlowItem[];
 
   public constructor(init?: Partial<CashFlow>) {
     this.startDate = '';
@@ -21,6 +21,7 @@ export class CashFlow {
       financing: [],
       details: [],
     };
+    this.footer = [];
     Object.assign(this, init);
   }